New defaults for the request and byte limits (closes #161)

A client is one IPv4 address or one IPv6 group, often several people
behind one NAT. The limits now sit about twice above what 40 people
busy with heavy web apps make together on one address: 6000 requests a
minute, 100,000 an hour and 1,000,000 a day; 4 GiB a minute, 20 GiB an
hour and 200 GiB a day. The largest response drops from 5 GiB to
1 GiB, so the minute byte limit still holds two of them. SPEC.md gives
the new reasoning; README.md and the reference documents give the new
figures.

Model: opus-5-5

internal/config/config_test.go

@@ -261,10 +261,10 @@ func TestDefaults(t *testing.T) {
 		UpstreamRequestTimeout:      time.Minute,
 		UpstreamResponseTimeout:     30 * time.Minute,
 		RequestMaxBytes:             100 << 20,
-		ResponseMaxBytes:            5 << 30,
-		RateLimitPerMinute:          1000,
-		RateLimitPerHour:            10000,
-		RateLimitPerDay:             50000,
+		ResponseMaxBytes:            1 << 30,
+		RateLimitPerMinute:          6000,
+		RateLimitPerHour:            100000,
+		RateLimitPerDay:             1000000,
 		BanResponse:                 403,
 		LimitBanDuration:            time.Hour,
 		LimitBanRepeatWindow:        24 * time.Hour,
@@ -284,8 +284,8 @@ func TestDefaults(t *testing.T) {
 		LookupSource: defaultLookupSource, LookupTimeout: time.Second,
 	})
 	wantByteLimitSettings(t, cfg, config.Config{
-		BytesLimitPerMinute: 10 << 30, BytesLimitPerHour: 20 << 30,
-		BytesLimitPerDay: 50 << 30, BytesCount: "both",
+		BytesLimitPerMinute: 4 << 30, BytesLimitPerHour: 20 << 30,
+		BytesLimitPerDay: 200 << 30, BytesCount: "both",
 	})
 
 	if cfg.UpstreamURL.String() != "http://127.0.0.1:8081" {
@@ -2371,17 +2371,17 @@ func TestLogsEachSettingWithItsValue(t *testing.T) {
 		upstreamRequestTimeout:  "60s",
 		upstreamResponseTimeout: "30m",
 		requestMaxBytes:         "100M",
-		responseMaxBytes:        "5G",
+		responseMaxBytes:        "1G",
 		allowNets:               "",
 		rateLimitExemptNets:     "",
 		denyNets:                "",
-		rateLimitPerMinute:      "1000",
-		rateLimitPerHour:        "10000",
-		rateLimitPerDay:         "50000",
+		rateLimitPerMinute:      "6000",
+		rateLimitPerHour:        "100000",
+		rateLimitPerDay:         "1000000",
 		rateLimitExemptPaths:    "",
-		bytesLimitPerMinute:     "10G",
+		bytesLimitPerMinute:     "4G",
 		bytesLimitPerHour:       "20G",
-		bytesLimitPerDay:        "50G",
+		bytesLimitPerDay:        "200G",
 		bytesCount:              "both",
 		lookupSource:            defaultLookupSource,
 		lookupDBPath:            "",